Method Validation for Multi-Pesticide Residue Determination in Chrysanthemum.

The chrysanthemum can be consumed in various forms, representing the "integration of medicine and food". Quantitative analysis of multi-pesticide residues in chrysanthemum matrices is therefore crucial for both product-safety assurance and consumer-risk evaluation. In the present study, a simple and effective method was developed for simultaneously detecting 15 pesticides frequently used in chrysanthemum cultivation in three matrices, including fresh flowers, dry chrysanthemum tea, and infusions. The calibration curves for the pesticides were linear in the 0.01-1 mg kg-1 range, with correlation coefficients greater than 0.99. The limits of quantification (LOQs) for fresh flowers, dry chrysanthemum tea, and infusions were 0.01-0.05 mg kg-1, 0.05 mg kg-1, and 0.001-0.005 mg L-1, respectively. In all selected matrices, satisfactory accuracy and precision were achieved, with recoveries ranging from 75.7 to 118.2% and relative standard deviations (RSDs) less than 20%. The validated method was then used to routinely monitor pesticide residues in 50 commercial chrysanthemum-tea samples. As a result, 56% of samples were detected with 5-13 pesticides. This research presents a method for the efficient analysis of multi-pesticide residues in chrysanthemum matrices.

Residue dissipation, transfer and safety evaluation of picoxystrobin during tea growing and brewing.

BACKGROUND: Picoxystrobin is a new osmotic and systemic broad-spectrum methoxyacrylate fungicide with a good control effect on tea anthracnose, so it has been proposed to spray picoxystrobin before the occurrence and onset of tea anthracnose during tea bud growth in order to protect them. However, there are few reports about the residue analysis method, field dissipation, terminal residue and risk assessment of picoxystrobin in tea. And there is no scientific and reasonable maximum residue limit of picoxystrobin in green tea. RESULTS: A rapid and sensitive analysis method for picoxystrobin residue in fresh tea leaf, green tea, tea infusion and soil was established by UPLC-MS/MS. The spiked recoveries of picoxystrobin ranged from 73.1% to 111.0%, with relative standard deviations from 1.8% to 9.2%. The limits of quantitation were 20 µg kg-1 in green tea, 8 µg kg-1 in fresh tea leaves and soil and 0.16 µg kg-1 in tea infusion. The dissipation half-lives of picoxystrobin in fresh tea leaf and soil were 2.7-6.8 and 2.5-14.4 days, respectively. And the maximum residue of picoxystrobin in green tea was 15.28 mg kg-1 with PHI at 10 days for terminal test. The total leaching rate of picoxystrobin during green tea brewing was lower than 35.8%. CONCLUSIONS: According to safety evaluation, the RQc and RQa values of picoxystrobin in tea after 5 to 14 days for the last application were significantly lower than 1. Therefore, the maximum residue limit value of picoxystrobin in tea that we suggest to set at 20 mg kg-1 can ensure the safety of tea for human drinking. © 2020 Society of Chemical Industry.

Nitenpyram in tea: Eco-friendly detection methodology and residue behavior.

Studies on nitenpyram determination and behavior within tea remain limited despite its widespread use as a neonicotinoid. An organic-saving analytical approach tailored for the detection of nitenpyram in tea was established. Nitenpyram was extracted by boiling water and cleaned up by Cleanert PCX solid-phase. The average recoveries were 75.1-94.5 %, with relative standard deviations (RSDs) of 0.7-8.6 % for saving 34.5-88.6 % organic solvent. The limits of quantification (LOQs) were 0.002 mg·kg-1 in fresh tea shoots, 0.005 mg·kg-1 in made tea, and 0.001 mg·L-1 in tea brew, satisfying the current minimum Maximum Residue Limit (MRL). Nitenpyram dissipated rapidly with half-lives of 1.2-1.4 days at the recommended dosage (27 g a.i. ha-1) in two locations. Remarkably, 20-110 % of nitenpyram was leached out from made tea in different brewing modes. This work provides insights into nitenpyram's rational application in tea cultivation and offers considerations to institutions tasked with unestablished MRLs in tea.

Temperature-Dependent Photoluminescence of Manganese Halide with Tetrahedron Structure in Anti-Perovskites.

The temperature-dependent photoluminescence (PL) properties of an anti-perovskite [MnBr4]BrCs3 sample in the temperature range of 78-500 K are studied in the present work. This material exhibits unique performance which is different from a typical perovskite. Experiments showed that from room temperature to 78 K, the luminous intensity increased as the temperature decreased. From room temperature to 500 K, the photoluminescence intensity gradually decreased with increasing temperature. Experiments with varying temperatures repeatedly showed that the emission wavelength was very stable. Based on the above-mentioned phenomenon of the changing photoluminescence under different temperatures, the mechanism is deduced from the temperature-dependent characteristics of excitons, and the experimental results are explained on the basis of the types of excitons with different energy levels and different recombination rates involved in the steady-state PL process. The results show that in the measured temperature range of 78-500 K, the steady-state PL of [MnBr4]BrCs3 had three excitons with different energy levels and recombination rates participating. The involved excitons with the highest energy level not only had a high radiative recombination rate, but a high non-radiative recombination rate as well. The excitons at the second-highest energy level had a similar radiative recombination rate to the lowest energy level excitons and a had high non-radiative recombination rate. These excitons made the photoluminescence gradually decrease with increasing temperature. This may be the reason for this material's high photoluminescence efficiency and low electroluminescence efficiency.

Distribution behavior of arsenate into α-calcium sulfate hemihydrate transformed from gypsum in solution.

Transforming gypsum into α-calcium sulfate hemihydrate (α-HH) provides a promising utilization pathway for the abundant amount of chemical gypsum. The transformation follows the route of "dissolution-recrystallization", during which the arsenic pollutant in gypsum is released into the solution, and hence raises the possibility of being distributed into the product of α-HH, a potential harm that has always been neglected. Investigation of the transformation process at neutral pH revealed that the arsenate ions in solution were distributed into α-HH and generated an enrichment of arsenic by 4-6 times. Arsenate ions distributed into α-HH by substitution for lattice sulfate, adsorption on α-HH facets and occupation for surface sulfate sites. While at higher concentrations, calcium arsenate coprecipitated with α-HH or even crystallized independently. Increasing temperature accelerated the phase transformation and restrained arsenate migration into α-HH due to the lag of distribution balance. The pH of solution modulated the dominant arsenate species and decreasing pH weakened arsenate substitution capacity for sulfate in α-HH. This work uncovers arsenate distribution mechanism during the transformation of gypsum into α-HH and provides a feasible method to restrain arsenate distribution into product, which helps to understand arsenate behavior in hydrothermal solution with high concentration of sulfate minerals and provides a guidance for controlling pollutants distribution into product.

Application and enantiomeric residue determination of diniconazole in tea and grape and apple by supercritical fluid chromatography coupled with quadrupole-time-of-flight mass spectrometry.

A chiral separation and residue determination method for diniconazole enantiomers in tea, apple, and grape was developed and validated by supercritical fluid chromatography coupled with quadrupole-time-of-flight mass spectrometry (SFC-Q-TOF/MS). The two diniconazole enantiomers were separated on a Chiral CCA column, and the chromatographic conditions (mobile phase proportion and modifier, column temperature, backpressure, and auxiliary solvent) were optimized. The optimal SFC-Q-TOF/MS conditions were selected as a mobile phase of CO2/isopropanol (IPA) (v/v, 96/4), flow rate at 2.0 mL/min, automated back pressure regulator (ABPR) at 2000 psi, column temperature at 25 ℃ and under electrospray ionization positive mode with the best auxiliary solvent of 2 mmol/L ammonium acetate in methanol/water (v/v, 1/1) at 0.20 mL/min flow rate. Residues in tea and fruit samples were extracted by acetonitrile/water (v/v, 4/1 for fruit and 2/1 for tea), purified by Cleanert TPT or Pesti-Carb solid phase extraction column, then analyzed by SFC-Q-TOF/MS with matrix-matched external standard quantification method. The elution order of diniconazole enantiomers on CCA column was R-(-)-diniconazole at first, and S-(+)-diniconazole at second. The standard curve concentration levels of R-(-)-diniconazole and S-(+)-diniconazole in samples ranged from 0.01 mg/L to 1.00 mg/L with the correlation coefficients greater than 0.99. The spiked recoveries of R-(-)-diniconazole and S-(+)-diniconazole in apple and grape at three levels of 0.005, 0.05 and 0.25 mg/kg were in the range of 69.8% to 102.1%, with relative standard deviations (RSDs) (n = 6) between 3.5% and 10.4%, and the limits of quantitation (LOQs) below 0.005 mg/kg. The spiked recoveries in black tea at three levels of 0.01, 0.10, and 0.50 mg/kg were in the range of 85.6% to 90.6%, with the RSDs (n = 6) ranging from 3.9% to 9.5%, and LOQ of 0.01 mg/kg. This residue analysis and determination method for diniconazole enantiomers in apple, grape and tea samples is convenient, reliable, and meets the residue analysis requirement. Also it is applicatied for the residue fates of R-(-)-diniconazole and S-(+)-diniconazole during the fresh tea leaves growing, green tea processing and black tea processing. The degradation half-times (DT50) between R-(-)-diniconazole and S-(+)-diniconazole in the fresh tea leaves growing were 2.9 d and 3.1 d, respectively. The concentrations of R-(-)-diniconazole and S-(+)-diniconazole decreased gradually with time and on the 14th day after application were lower than 10% of the initial concentration. The average enantiomer fractions (EFs) of R-(-)-diniconazole and S-(+)-diniconazole at 2 h, 2, 5, 7, 10 and 14 d after application in fresh tea leaves were 0.505, 0.526, 0.523, 0.558, 0.453 and 0.489, respectively. This result is similar to the result of our last research for the enantiomers of cis-epoxiconazole-another triazole fungicide residues in fresh tea leaves. And in the whole black tea processing, 37.1%-49.3% and 35.9%-57.9% of R-(-)-diniconazole and S-(+)-diniconazole decreased, respectively. The total processing factors (PFs) of R-(-)-diniconazole and S-(+)-diniconazole for the black tea procedure were 0.507-0.629 and 0.421-0.641, respectively. The EFs of R-(-)-diniconazole and S-(+)-diniconazole in black tea processing ranged from 0.432 to 0.532. However, in the whole green tea processing, 22.3%-32.6% and 21.7%-40.3% of R-(-)-diniconazole and S-(+)-diniconazole decreased, respectively. The difference between black tea and green tea is nearly 15%, and in green tea is less decreased than in black tea. The total PFs of R-(-)-diniconazole and S-(+)-diniconazole for the green tea procedure were 0.674-0.777 and 0.597-0.783, respectively. The EFs of R-(-)-diniconazole and S-(+)-diniconazole in green tea processing ranged from 0.473 to 0.504. The PFs illustrated that for R-(-)-diniconazole and S-(+)-diniconazole decrease, the rolling and fermentation were the critical steps in black tea processing, and the rolling was the critical step in green tea processing, respectively.